Railway-traffic-controlling apparatus



March 9 1926. 1,575,633

R. A. MCCANN RAILWAY TRAFFIC CONTROLLING APPARATUS Filed Se t; 8, 1925 I J a afi a ATTORNEY Patented Mar. 9, 1926.

UNITED STATES PATENT OFFICE.

RONALD A. MCGANN. SWISSVALE, PENNSYLVANIA, ASSIGNOR T UNION SWITCH & SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENN SYLVANIA.

RAILWAY-TRAFFIC-CONTROLLING APPARATUS.

Application filed September 8, 1925. Serial No. 54,933.

To all whom it may concern:

Be it known that I, RONALD A. MCCANN, a citizen of the United States, residing at Swissvalc, in the county of Allegheny and State of Pennsylvania, have invented cer-,

tain new and useful Improvements in Railway-Tratfic-Controlling Apparatus, of which the following is a specification.

My invention relates to railway traflic con trolling apparatus, and particularly to apparatus of the type wherein train carried governing mechanism is controlled by energy received from the trackway. More specifically the present invention relates to the trackway portion of such apparatus.

I'will describe one form of apparatus em bodying myinvention, and will then point out the novel features thereof in claims. The accompanying drawing is a diagrammatic view showing one form of railway traffic controlling apparatus embodying my invention.

Referring to the drawing,the reference characters 17 17 designate the track rails of a railway along which traffic normally movesin the direction indicated by the ar row. These rails are divided by insulated joints 2, into electrically isolated track sections of which only one complete section A-B is shown in the drawing. This section includes a switch 0 having a normal position wherein trafiic moves from point A to point B, and a reverse position wherein trafiic is diverted from the sectionAB to a branch track H. I Each track section is provided with a track circuit comprising a source of alternating current connected across the rails at the exit end of the section, and a track relay having a winding connected across the rails at the entrance endof the section. As here shown the source of track circuit current for section AB is a transformer D, the primary 12 of which is connected with a transmission line G which is constantly supplied with alternating current by a genorator F. The secondary 13 of transformer D is connected across the rails through the medium of pole changing contacts 14 and 15 of a line relay R. The track relay for section AB is designated by the reference character T and the track relay for the section immediately in advance of section A- B is designated by the reference character T Line relay R is controlled by contact 16 of track relay T so that relay R as energized when traflic conditions in advance of section AB are safe but not when traflic conditions in advance in this section are unsafe. The track circuit current which is supplied to the rails of section A-B is of normal or reverse relative polarlty according as relay R is energized or deenergized.

A first impedance 3- is connected across the rails adjacent the entrance endof section AB, a second impedance 3 is connected across the rails in the rear of switch 1 current flows from the right-hand terminal of secondary 5 of transformer E, through wire 19, contact 7 which is closed only when-switch C is in the normal position, to the middle point of impedance 3, then through the rails 17 and 17 in multiple to impedance 3 and from the middle point of this impedance through front contact 6 6 of relay R to the left-hand terminal of secondary 5. Loop current is thus supplied to the two rails in multiple from the entrance end to the exit 3 end of section A-B. I will now assume that line relay R is de-energized and that switch C is in the normal position. Current then flows from the right-hand terminal of the middle point of impedance 3", and from this impedance through the track rails in multiple to impedance 3, from the middle point of which the current flows through wire 20, and back contact 6 6 of relay R to the secondary 5. Under this condition it will be seen that loop-current from transformer E flows through the rails of section AVB between impedances 3 and 3 only. It will also be seen that the track circuit current supplied to this section is of reverse relative polarity because the pole-changing contacts 14 and 15 of relay R are reversed.

The trackway apparatus herein illustrated is intended for co-operation with train ,car-

secondary '5 through wire 19, contact 7 to ried mechanism in such manner that, when the train occupies a portion of track which is supplied with track circuit current of normal relative polarity and also with loop current, a proceed indication is given on the train; when the track occupied by the train is supplied with track circuit current of reverse relative polarity and also with loop current, a caution indication is given on the train; and when the supply of either track circuit current or loop current is discontinued a stop indication is given on the train.

It will be seen from the foregoing that when relay R- is deenergized and the switch G is in the normal position, a train passing through section AB will receive a caution indication between in'ipedances 3 and 3 because the track circuit current is of reverse relative polarity, and a stop indication between impedances 3 and 3 because of the absence of loop current.

Vith the apparatus thus far described it will be seen that when switch C is reversed contact 7 will be open thereby discontinuing the supply of loop current from transformer 12, and so causing a stop indication on a train. 7 It is desirable however to be able to reverse switch C after a train has passed this switch without causing a stop indication aboard the train, and auxiliary means are accordingly provided for supplying loop current to the track rails between switch C and the exit end of the section. Assuming that relay R- is energized and that switch C is reversed, current flows from the righthand terminal of secondary 5 of transformer E, through wire 18-, front contact 8 of relay R, resistance 9, contact 10 which is closed only when switch G is reversed, and thence directly to rail 17: a portion of this current also flows to rail 17 through contact 11 which is closed only when switch C is reversed; the current then flows through the two rails in multiple to impedance 3. and from the middle point of this impedance through contact 6*-6 of relay R to the lefthand terminal of secondary It will be seen therefore that when a train occupies section A--B between the switch C and point B, and switch C is reversed behind the train, a proceed indication will be given on the train because track circuit current of normal relative polarity and loop current are both supplied to the portion of the track occupied by the train.

It will be noted that when switch C is reversed the right-hand terminal of secondary '5 of transformer E is connected with the track rails adjacent switch C through a front contact 8 of relay R. Heretofore, it has been suggested to connect the right-hand ter- 'minal of secondary 5 with resistance 9 and contact 10 when switch C is reversed, leaving out contact '8 of relay R, but this arrangement was found to permit a false proceed indication aboard a train between inipedance- 3 and switch C when line relay R- is (ls-energized. That is to say, current could flow from the righthand terminal of secondary 5 through contact 10 to the track rails adjacent switch C, then along the rails in multiple to impedance 3", and from the middle point of this impedance through wire 20 and back contact 6 6 to the lefthand terminal of secondary 5. This current would fiow through the track rails in the opposite direction, at any given instant, to the normal direction of loop current flow, and the track rails being supplied with track circuit current of reverse relative polarity because of the de-energization of line relay R, a proceed indication would be given aboard a train between impedance 3 and switch C. By means of my invention this false proceed indication is impossible because when relay R is de-energized the supply of loop current to the rails is discontinued at contact 8. Consequently, when switch C is reversed and relay R is de-energized, a stop indication is given aboard a train at all points in section A-B.

Although I have herein shown and described only one form of apparatus embodyingn'iy invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims withoutdeparting from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a section of railway track containing a switch, means operating when said switch is in normal position to supply train governing current to the rails of said section in multiple from the entrance end to the exit end if traffic conditions in advance of the section are safe but only from the entrance end to a point in the rear of said switch if tralfic conditions in advance of the section are unsafe, said means operating when said switch is reversed to supply train governing current to the rails of said s ction from said switch to the exit end if trafiic conditions in advance of the section are safe but to prevent the supply of said train governing current to any portion of said section when the switch is reversed and traffic conditions in advance of the section are unsafe.

2. In combination, a railway track comprising a section containing a switch, a first impedance connected across the rails adjacent the entrance end of said section, a second impedance connected across the rails of said section in the rear of said switch, a third impedance connected across the rails adjacent the exit end of said section, a relay, means for energizing said relay when trailic conditions in advance of said section are safe but not When traflic conditions in advance of said section are unsafe, a source of train governing current, means for connecting the first terminal of said source through a front contact of said relay With said third impedance and through a back contact of said relay With said second impedance, means for connecting the second terminal of said source with said first impedance through a contact which is closed 1 only when the switch is in reverse position 15 and a front contact of said relay.

In testimony whereof I afiix my si nature.

RONALD A. McclNN. 

